1. Field of the Invention
This invention relates generally to a detachable sideshade for spectacles, and more particularly concerns a sideshade that is removably attachable to a temple of spectacles such that the wearer of the spectacles is not required to remove the spectacles in order to attach the sideshade to or detach the sideshade from the temple of the spectacles. The detachable sideshade is optical or near-optical quality such that the sideshade does not degrade or distort details in the peripheral viewing area of the wearer and may be tinted for reducing peripheral glare.
2. Prior Art
In the field of optical wear, a wide variety of sunglasses and goggles have been developed over the years for various purposes, depending upon the specific function of the sunglasses or the activity involved while wearing the sunglasses. Optical wear has been created to reduce glare from point sources of light, such as from oncoming cars or from direct sunlight. Optical wear has also been created to reduce the glare from broad regions of high illumination, such as office lighting, sky glare, and ground glare. Optical wear also has been developed for directing sight into specific fields of vision. This type of eyewear enables the viewer to assume a correct posture or position for carrying out a physical activity; the great majority of the prior art in this application has been in developing golfing glasses. Finally, optical wear has been designed to reduce visual stress in contrasting lighting situations and to enhance feature extraction in different fields of vision, these types of optical wear can be useful during physical activities where it is desirable to see a specific object against a background, such as golfing, fishing, hunting or other outdoor recreational activities.
One area that prior art has not addressed is the situation encountered by pilots of jet aircraft, which are flown typically at altitudes between 35,000 and 45,000 feet. At these heights during the day, the illumination from outside the cockpit is especially high. The high illumination comes from scattered light from both the sky and clouds. Indeed, when flying over clouds, pilots typically experience illumination values around 9,000 lux even when they are not looking in the direction of the sun. By contrast, under these external lighting conditions, the illumination of the instrument panel can be typically around 30 lux. In this case, the ratio between the outside illumination to that of the instrument panel is 300 to 1. Making transitions between these two contrasting fields of illumination can be stressful to the eyes.
Of the variations of sunglasses disclosed in prior art, none has satisfactorily solved the problem of balancing the illumination between outside and inside the cockpit—a problem that pilots flying at altitude encounter. Ordinary dark sunglasses do not solve this problem; while they do reduce the outside illumination to a comfortable level for the pilot, they can render the instrument panel too dark for the pilot to discern readings on the gauges. On the other hand, vignetted sunglass lenses assist in the overall balancing of illumination outside the cockpit with that of the instrument panel, but they permit too much light to enter a pilot's eyes, thus causing glare when the pilot views the instruments.
The limitations of prior art described above highlight the need for sunglasses that specifically address the two and often related problems that many jet pilots routinely encounter when flying at altitude: that is, (1) the contrast in illumination causes stress on the pilot's eyes resulting from the eyes having to adjust back and forth between the high illumination from outside the cockpit and the low illumination from the instrument panel; and (2) the glare caused by the high illumination can degrade the ability of the pilot to adequately see the instruments. Moreover, these two problems are exacerbated as the pilot ages.
To fully understand the problem the specially tinted lens solve, it is helpful to define the difference between the horizon and the horizontal plane in which the aircraft is flying. The horizon is plane tangent to the earth's surface at an observer's position and the horizontal plane is perpendicular to the vertical axis to the earth. Between 35,000 ft and 45,000 ft the horizon is approximately 3.3° to 3.8° below the horizontal plane. Consequently, whenever the aircraft is above a uniform layer of cloud that extends to the horizon, the illumination from that cloud layer originates from below the horizontal plane.
The illumination that a pilot experiences when flying at these high altitudes can be significantly different from that experienced by a person on the ground. For example, when pilots fly above the clouds, the illumination experienced when they look horizontally and below is typically greater then when they look above the horizontal plane. This high illumination at and below the horizontal plane poses a unique problem for pilots when they look at the instruments, in that the high illumination from outside the cockpit can be relatively close to their intermediate field of vision of the instruments. The reverse tends to be the case for a person on the ground, where the illumination generally increases when looking upwards.
The specially tinted lens, when adapted to sunglasses, enable a pilot to easily view outside the cockpit into high illumination and simultaneously view the instrument panel in low illumination without the eyes having to compensate for the previously described problems of adjustment and glare. The specially tinted lens reduces visual stress to the eyes by greatly reducing the difference in illumination as received by the eyes between lighting outside the cockpit and the instrument panel. In addition, this reduction in light received by the eyes from outside the cockpit greatly reduces glare that can impair the pilot's vision of the instrument panel.
The specially tinted lens addresses the specific and unique condition present in the cockpit of a jet aircraft where the instrument panel and nose of the aircraft block the high illumination from outside the cockpit from entering the intermediate section of the lens.
Under some situations, disability glare can be so great from the illumination outside the cockpit that details of the instruments cannot be read without blocking or greatly attenuating the outside illumination. The specially tinted lens greatly reduce glare experienced by pilots and effectively eliminate disability glare by attenuating the high illumination that enters through the front of the sunglasses. However, even when wearing these sunglasses with the specially tinted lenses, there still can be high illumination that enters the pilot's eyes from the sides of the spectacle frames, causing what is called discomfort glare. Discomfort glare does not inhibit the pilot from reading details on the instrument panel, but it creates an uncomfortable and/or distracting viewing situation. This discomfort glare can be mitigated by use of sideshades with sunglasses with the specially tinted lenses. A reference to disability and discomfort glare is given in the Introduction to Visual Optics, Alan H. Tunnacliffe 4th Edition 1993. Association of British Opticians, Canterbury, ISBN 0-900099-28-3, 603 pages.
The detachable sideshades disclosed herein are novel in that they can be installed and removed without the pilot having to remove his or her sunglasses or headset, thus creating a minimum amount of distraction for the pilot. Moreover, either or both sideshades can be worn as the lighting situation requires. A pilot, for instance, may wear just one sideshade—the sideshade that faces the outside of the cockpit. The detachable sideshades may be optical or near-optical in quality and will enable the pilot to maintain peripheral vision. The optical density of the sideshades may be such that the light transmitted through them will be approximately the same as that transmitted through the distant portion of the specially tinted lenses.
In the field of eyewear concerned with the peripheral area of one's vision, there are numerous known devices, such as sideshades, sideshields, side guards, etc. Sideshades reduce the peripheral illumination to a comfortable level, which tends to enhance one's vision in the forward direction. Sideshields have the primary purpose of protecting the eyes, generally from flying objects. Sideshields can also protect one's eyes from wind and high intensity illumination, such as laser light. In addition, sideshields can also function as sideshades.
In the field of sideshades and sideshields for spectacles, there is a wide range of prior disclosed art that primarily addresses the need to protect the eyes of the spectacle wearer from injury from flying objects, high illumination or dangerous radiation. In general, earlier prior art has disclosed sideshields that are non-optical quality and rigid and that require the wearer to remove his or her spectacles to either install or remove the sideshields. Installation and removal of the sideshields disclosed in the prior art are tedious, and therefore, the wearer would have to remove his or her spectacles to install or remove these sideshields. The detachable sideshades disclosed herein may be optical or near-optical in quality, are light, can be flexible and do not require the wearer to remove his or her spectacles when installing or removing them.
Sideshields that meet impact resistance standards (e.g., American National Standard Institute, ANSI, Z87.1) must be securely mounted onto the eyewear in question, and therefore, do not lend themselves to being installed or removed while an individual is wearing his or her eyewear. Universal sideshields that fit a broad range of frame shapes and sizes are typically more labor intensive to install and remove than sideshields that are frame type and size specific. Sideshields that fall into this category include those of Simmons (U.S. Pat. Nos. 5,748,278, 6,393,609, 6,832,389, and 7,013,495). These sideshields are not optical quality nor are they easily installed or removed.
It is therefore desirable to provide a detachable sideshade that is easily installed or removed from the frame of sunglasses.
It is therefore further desirable to provide a detachable sideshade that may easily installed or removed while an individual is wearing his or her eyewear.
It is yet further desirable to provide a detachable sideshade of optical or near-optical quality as to not distort or degrade a wearer's peripheral vision.
It is yet further desirable to provide a detachable sideshade that is tintable.
It is yet further desirable to provide a detachable sideshade being transparently tintable to reduce glare caused from the high illumination in a wearer's peripheral vision.
It is yet further desirable to provide a detachable sideshade that conforms to the outside of the spectacle frame to prevent light from entering the wearer's eyes from the region between the sideshade and the eyewear frame.
It is yet further desirable to provide a detachable sideshade that vertically extends above and below the temple and conforms to the wearer's head to prevent light from entering the wearer's eyes from areas above and below the temple.